High frequency resistance device



June .1942. J. MI VAN BEUREN 2.286,029

- HIGH FREQUENCY RESISTANCE DEVICE Filed June 9, 1941' 5 Sheets-Sheet 1 June 9, 1942. J. M. VAN BEUREN 2,286,029

HIGH FREQUENCY RESISTANCE DEVICE Filed June 9, 1941 3 Sheets-Sheet-Z Fae.

4- INVENTOR HTTORN 3 Sheets-Sheet 5 Fl G. 9.

J. M. VAN BEUREN' HIGH FREQUENCY RESISTANCE DEVICE Filed June 9, 1941 June 9, 1942.

INVENTOR. %.M3W

ATTORNEY.

OUTPUT Patented June 9, 1942 UNITED STATE s PATENT OFFICE amaze HIGH FREQUENCY RESISTANCE DEVICE John M. van Benren, Boonton, N. 1., assignor to Measurements Corporation, Boonton, N. 1., a corporation of New Jersey Application June 9, 1941, Serial No. 391,351

15 Claims.

This invention relates to improvements in the construction and assembly of resistance devices, such as attenuators associated'switching mechanism and the like, used in high frequency measuring circuits or networks.

-Although not in all of its aspects so limited, this invention is particularly concerned with arrangements for so mounting andelectrically conator comprising a plurality of pads each including a plurality of resistors, which individually, and collectively because of their interconnections and relative positions, have inappreciable inductance and capacity at high frequencies with each other and with thepads so mounted or positioned with respect to each other that, regardless of which of the resistors is brought into circuit by switching means. there always obtain the same relations between the individual resistors of the pad in circuit and between the resistors of the pad in circuit and the other pad, or there always obtain the same relations between the individual resistors of the pad in cir-' cuit and between them and the resistors of the pad out of circuit, that the phase angle of the attenuator remains substantially constant for all positions of the switching mechanism. 1

This invention still further resides in the features of construction, combination and arrangement hereinafter described and claimed.

For precise results at ultra high frequencies, particularly of the order of 200 megacycles and upward per second, it is often necessary to obtain known voltages of constant value over a wide range of frequencies. This is particularly neces sary where precise measurements are concerned.

The addition or subtraction of inductance in the associated circuits and switching mechanism,

even the change caused by adding or subtracting I as little as one inch of conductor whose inductive elects have not been annuled, will often gieatly impair the constancy of the resulting "voltage due to the development of standing waves on the conductor.

The present invention serves to overcome such inaccuracies by providing ciently reduced as to permit of substantially preor discs 2 suitably drilled an arrangement in. which indiictive and capacity eifects are sulldetermined output potentials over a wide range of frequencies.

For an understanding of this invention, reference is made to the accompanying drawings, in which:

Fig. 1 shows a plan view of the assembled combined resistance attenuator and switch.

Fig. 2 shows a side elevation with resistor en closing cap portion removed.

Fig. 3 shows an elevational view, in perspective, of the frame side member whichforms the resistor enclosing path.

Fig. 4 is an end view of the rotatable switch drum member looking at the output end.

Fig. 5 shows a modified form of switch drum.

Fig. 6 is an end view of the modified drum of Fig. 5, looking at the output end.

Fig. Iris a partial view of the input end of the' modified drum of Fig. 5.

Fig. Bshows, in perspective, one of the drum units of Fi 5.

Fig. 9 is' a combined schematic wiring diagram, and development view of the switch drum of Figs. 1,2, and 4.

In Figs. 1, 2, comprising metallic cylinder I to which'is secured in any suitable manner, such as for example by soldering, a multiple of metal washers to support coaxial conand 1. Cylinder l is seductor tubes 3. l, 5, 5.

end plate 0 and cured in shaft 0 journaled in adapted for convenient rotation by knob II or any other suitable means.

End plates 9 and II are secured to the ion! tudinal frame members I! which contain longitudinal semi-circular recesses it and transverse semi-circular recesses ll. Each of the frame members .l! are provided with cap members Ila containing corresponding semi-circular recesses lid and Ila.

Frame members It are drilled to accommodate insulating bushings I! which in turn support screws I. out of electrical contact with the frame members. Screws ll serve the double purpose of securing contact springs l1 and forming a path of electrical conductivity between the springs i1 and terminals of resistors I. These resistors are preferably of a non-inductive type, such as carbon, of a sufficiently high resistance value as to furnish the desired degree of electrical attenuation, they are constructed in small cylindrical form and provided at each end with a conducting lead or terminal It.

The resistors II are preferably arranged in 1' formation with a series of horizontally and 4, a rotatable drum member a resistors having a vertically disposed resistor connected by its upper terminal to the-terminals i3 between each pair of horizontally disposed resistors and to the conducting screws it, the lower terminals of the vertical resistors are connected to frame grounding pins 20 mechanically and electrically secured to the frame member i2. In

. this arrangement both the inductive and caof the frame. The diagrammatic arrangement.

shielding actions Even though so called 'noninductive carbon resistors are used, even these have appreciable inductance at frequencies in theorder of 100 ,megacycles or more and this inherent inductance is reduced by surrounding the resistors i8 i2 and, Ho.

Shaft 8 is partially located within and secured to cylinder I and provided with a shoulder acting on end plate 3 and suitable means to take up unnecessary longitudinal motion such as pivotal screw 2i operating in a recess in the end with a close fitting metal shell,

of shaft 8 and locked in place by means of lock- .nut 22.

Coaxial tubes 3, 4, 5, 6, and 1 each contain a conductor 24, 25, 26, 21, and 23-respectivelyof smaller diameter than the bore of the tube and insulated therefrom, at the ends, by means of centering insulating washers 23. These conductors may be in the form of rodsthreaded at theends, as shown, and locked in place by rneans of nuts which also serve to secure drum contact members 30 in operating position co-- acting with -stationary contacts H. In the case of short rod 23 the tube may be omitted and disc or washer 2 will serve to act as the coaxial tube for this particular rod.

, Opposite the output end of the drum there is located an insulating block 3| to which are suitably secured a pair of stationary contacts 32 and 33 coacting with output contacts 30a located on the output end of the drum as better illustrated in Fig. 4. A connection may be made to either or both of stationary contacts 32 and assaoaa case of a single attenuator system and switch only one-half of the resistors l8 will be required and they will then be located on one-side only of a single attenuator system; and switch'is clearly indicated in Fig. 9.

In Figures 5 and 6 there is shown a modified form of rotatable drum comprising a series of metallic sectional drum members 35, more clearly shown in perspective in Fig. 8, having a specing shoulder 36, conductor containing holes 31 .and shaft mounting hole 38. Instead of shoulder 36 spacing washers may be used.

The required number of drum members may be secured to an end-threaded shaft 8a (Fig. 5) by means of lock nuts 33 and the shaft mounted in' a suitable modified frame similar to and out of electrical contact with the drum members 35. The drum members 35 provide. in this case, the surrounding shield for the con ductors 4i and 42. These conductors terminate at one end, respectively, in the spaces between the drum members 35 at their respective contacts 43 and 44 secured thereto by riveting or otherwise and coacting with a pair of stationary contacts similar to the single stationary contact arrangement shown at ll in Fig. 1, with the exception that when as in the present case there is used a balanced line consisting of two conductors. instead of the single conductor arrangement previously described, then one of each pair of sta- 33 respectively to utilize the output of either or both of the attenuator systems as desired.

Inorder to thoroughly ground every part of the rotatable drum at short intervals of lengthv contact springs 34, electrically contacting washers or discs 2, are mechanically secured to, and in. electrical contact with, frame members l2 by means of a screw or rivet or any other suitable manner.

It will be readily understood that due to the positioning ofcoaxial tube contacts 30 and coacting stationary contacts I! relative to output contacts 30a there will be but one coaxial tube conductor in circuit at one time on each side of the drum as the drum is rotated to select the desired point of contact between the resistors. It will also be understood that'the drum as shown in Figures .l, 2, and 4 contains a duplicate set of coaxial tubes and associated moveable and stationary contacts for the purpose of providing a double or balanced attenuator system and switch, and that a single attenuatorsystem and corresponding switch may be constructed with only one-half the number of coaxial tubes and moveable contacts shown in Figures 1 and 4.,

tionary contacts, as in this case required; is me- .chanically secured to but insulated from the frame'member I2 of Fig. Land these additional contacts are all connected together to form the return circuit of the balanced line. The use of a balanced line in lieu of the coaxial tube cable of Figures 1, 2, 4 and 9, is optional and in any case provides similar shielding functions.

At the output end of the drum of Fig. 5,'more clearly shown in Fig. 6, there is provided a single insulating washer 45 which supports all of the output contacts 43 and 44; andtheir associated rod conductors 4i and .42 to which they are riveted or otherwise secured, out of electrical contact with the drum members 35. In this case a pair of stationary output contacts are required at the output end coacting with the pairs of drum contacts 43 and 44 in somewhat similar arrangement to the single stationary contact shown at 32 in Fig. 1. Grounding contact springs, similar to springs 34 of Fig. 1, may be used in conjunction with the drum -of Fig. 5, for electrically grounding each drum member 35 to the frame i2.

Fig. lis indicated, but this diagramwill also serve to illustrate the electrical connections required with the balanced line arrangement of in which case only one side of longitudinal frame member l2 need be recessed and only one recessed cap member i2a will be required. In t e the drum shown in Fig. 5, provided the return circuit of grounded shields 2, 3, 4, 5, 6, 1, 46 and 41 and groundedpins 20 is obtainedwith a second conductor placed within but insulated from the shields and casing.

Input terminals 89 and 69 may be connected to a signal generator or any other source of ultra high frequency current and by rotating the drum until [the proper coaxial switch cable comes into electrical contact position with the proper reat its other end to a return circuit, said recesses rorming a substantially close fitting inductance short-circuiting sheath for each of said resistance units. and means for electrically tapping the junction between each pair of said serially connected resistance units comprising a shielded conductor connected to the output terminal.

as shown, in its characteristic or surge impedance.

by means of a suitable resistor I.

For purposes of clarity and definition it is understood that a contaminated current is one containing parasitic or spurious potential peaks developed by standing waves formed on an improperly terminated line, these parasitic or spurious peaks of potential may be practically annuled by shielding the. conductors and terminating the electrical line which they form, with a resistor of substantially the same value as that of the characteristic or surge impedance of the line.

This invention is not limited to the exact construction and circuit arrangement herein shown and described, but the same principles may be employed in similar devices of diflerent construe? tion.

What I claim is:

1. An ultra high frequency attenuator comprising a shielding frame, a recess within said frame containing a multiple of resistance unitsserially connected with an input terminal, a second recess within said frame containing a resistance unit connected at one end between a pair of said first mentioned resistance units and at its other end to a return circuit, said recesses forming a substantially close fitting inductance short-circuiting sheath for each of said resistance units,

cal junction between each pair of said serially connected resistance units.

2. An ultra high frequency attenuator comprising a shielding frame, a recess within said frame and means for tapping the circuit at the electricontaining a multiple of resistance units coaxially disposed with respect to each other and serially connected with an input terminal, a multiple of recesses within said frame disposed at right angles to said. first mentioned recess and each containing a resistance unit connected at one end between a pair of said first mentioned resistance units and at its other end toa return circuit, said recesses forming a substantially close fittingv inductance short-circuiting sheath for each of said resistance units, and means for-electrically tapping the Junction between each P of said serially connected resistance units.

3. An ultra high frequency attenuator comprising a shielding frame forming one side of a circuit, a recess within said frame containing a multiple of resistance units serially connected with an input terminal, a second recess within said frame containing a resistance unit connected at one end between a pair of said first mentioned resistance units and at its other end to said frame, said recesses forming a substantially close fitting inductance short-circuiting sheath for each of said resistance units, and means for electrically tapping the junction between each pair of said serially connected resistance units.

4. An ultra high frequency attenuator comprising a shielding frame, a recess within said frame containing a multiple of resistance units serially connected with: an input terminal, a

second recess within said frame containing a resistance unit connected at one end betweena pairofsaidfirstmentioned resistanceimitsand 5. An ultra-high frequency attenuator system comprising a multiple of resistors serially connected with an input terminal, a second resistor disposed at right angles to said first mentimed resistor and connected at one end between a pair of said first mentioned resistors and at its other end to a return circuit, means comprising a rotary drum containing a shielded line for electrically tappin the junction formed by each pair of said serially connected resistors to provide an output circuit, a return circuit for said output circuit. connected to said first mentioned return circuit, and a resistor of substantially the same value as'the surge impedance of said system connected in shunt across the terminals of said output circuit.

6. An ultra high frequency attenuator system comprising a multiple of resistors serially connected, a second set of resistors each connected at one end between a pair of said first mentioned resistors and at the other end to a return circuit, means for tapping the circuit at the electricaljunction formed by each pair of said serially connected resistors comprising a drum containing a plurality of shielded conductors to form an output circuit, a return circuit for said output circuit connected to said first mentioned return circuit, and a resistor of substantially the same value as the surge impedance of said sys-. tem connected across the terminals of said output circuit.

7. 'The'combination in a resistance attenuator of a frame consisting of side members supported by end plates, input, output and return circuit terminals supported by said frame, a recess within one of said side members containing a plurality of ,resistors in series connected to said input terminal, a multiple of resistors each connected at one end to the junction between each pair of said series resistors and at their opposite ends to said frame, a rotatable drum journ'aled in said end plates and provided with shielded conductors, and means for connecting said series resistors and at their opposite ends to said,

frame,.a rotatable drum journaled in said end plates and provided with shielded conductors, and means for connecting said shielded conductors to the iunction between said series and said multiple resistors and to said output terminal.

9. The combination in a resistance attenuator of a frame consisting of side members supported by end plates, input, output and return circuit terminals supported by said frame, a recess within one of said side members containing a plurality of resistors in series connected to said ininput, output and return circuit terminals each Junction of said circuit, and a plurality of shielded conductors put terminal, a multiple of resistors each connected at one end to the junction between each pair of said serdes resistors and at their opposite ends to said frame, a rotatable drum Journaled in said end plates and provided with shielded conductors, means for connecting said shielded conductors to the junction between said series and said multiple resistors and to said output circuit terminal, an output circuit connected to said output and retum circuit terminals and a resistor connected across the output circuit to substantially nullify parasitic potential peaks.

10. In combination a resistance attenuator comprising a plurality of resistors serially connected in a shielded input circuit, a multiple of resistors each connected at one end to the junction between each pair of said series resistors and at their opposite ends to a common return circuit, means for tapping said input circuit at arranged to be moved into contact position to connect one of said circuit.

12. In combination a resistance attenuator comprising aplurality of resistors serially connected in a shielded input circuit, a multiple of resistors each connected at one end to the junction between each pair of said series resistors a shielded output junctions with said output and at their opposite ends to a common return circuit, means for tapping said input circuit at each Junction of said resistors, a shielded output circuit, and a drum member comprising a plurality of shielded conductors rotated'into suitable position to said junctions with said output arranged to be connect one of circuit.

13. In combination a resistance attenuator comprising a plurality of resistors serially connected in'a shielded input circuit, a multiple' of resistors each connected at one end to the junction between each pair of said series resistors and at their opposite ends to a common return circuit, means-for tapping said input circuit'at each junction of said resistors,- a:shielded output circuit, and a rotatable drumii-prov-ided with a plurality of shieldedconductors arranged to be rotated into position to individually connect one of said Junctions with said output circuit. 1 14. In combination aresistance attenuator comprising a plurality of series resistors in' a shielded input circuit, a multiple of resistors each connected at one end to the junction between each pair of said series resistors and at their opposite ends to a common return circuit, means for tapping said input circuit at each Junction of said resistors including stationary contact clips, a shielded output circuit provided with stationary contact clips, a movable member supporting a plurality of shielded conductors provided at eachend with contact clips, and means for moving the contact clips of said shielded conductors into contact with the stationary clips of said output circuit.

1'5. In combination a resistance attenuator comprising a plurality of series resistors in a shielded input circuit, a multiple of resistors each connected at one end to the junction between each pair of said series resistors and at their opposite ends to a common return circuit, means for tapping said input circuit at'each junction of said resistors including stationary contact members, a shielded output circuit provided with stationary contact members, a rotatable member supporting a plurality of shielded conductors 01 various lengths and, provided at both of their respective ends with contact members, and means forrotating the shielded conductors and their respective contact members into contact with their corresponding said stationary contact members of said output circuit.

JOHN'M. via ,BEUREN. 

